Branched chain butyl formaldehyde mercaptals



United States Patent BRANCHED CHAIN BUTYL FORMALDEHYDE MERCAPTALS BillyDale Vineyard, St. Louis, Mo., assignor to Monsanto Company, St. Louis,Mo., a corporation of Delaware No Drawing. Filed Feb. 6, 1967, Ser. No.614,038 Int. Cl. C07c 149/10; Cm 1/38 U.S. Cl. 260-609 2 Claims ABSTRACTOF THE DISCLOSURE Branched-chain alkyl formaldehyde mercaptals which areuseful as antiwear additives in lubricating oils.

This invention relates to certain new formaldehyde mercaptals and theiruse as antiwear additives in lubricating oil compositions.

As a result of the trend towards lower ash-containing lubricating oilcompositions primarily through the use of non-metallic detergents, theability of such compositions to control the wear of vital engine parts,for example, the valve train assembly, has become more difiicult. As aresult, the use of metal-containing antiwear and/or extreme pressure(E.P.) additives has been increased in order to overcome theshortcomings of the non-metallic detergents. Obviously, such a solutionof the wear problem is not consistent with the desire for a completelynon-metallic formulation.

Accordingly, it is an object of this invention to provide certainnon-metallic antiwear and/or E.P. additives which for convenience arehereinafter merely referred to as antiwear additives. It is a furtherobject of this invention to provide non-metallic antiwear agents whichcan be substituted for present metallic antiwear additives, for example,zinc phosphorodithioates, to provide nonmetallic, ashless or low-ashlubricating oil compositions.

The formaldehyde mercaptals of the present invention are those representby the structure where R and R are each independently branched-chainalkyl radicals having from 3 to 4 carbon atoms. The mercaptals of thisinvention can be prepared by reacting formaldehyde with a suitablemercaptan by procedures known to the art. The following examples willillustrate typical preparations of the mercaptals of this invention.Parts are parts by weight.

Example 1 Into a suitable reaction mixture there was charged 180 parts(2.0 moles) of tert.-butyl mercaptan and 30 parts (1.0 mole) ofparaformaldehyde. Hydrogen chloride gas was bubbled through this mixturefor 3 hours while maintaining the reaction mass at a temperature 'of -30C. After completion of the hydrogen chloride addition, two layersformed, the lower of which, the aqueous layer, was removed. The organiclayer was then extracted with hexane, washed with water and dried, afterwhich the hexane was stripped and the remaining product frac tionated togive 170 parts of di-tert.-butyl formaldehyde mercaptal and had an indexof refraction, n of 1.4903.

Example 2 The procedure of Example 1 was repeated using 125 parts (1.4moles) of sec.-butyl mercaptan and 22.5 parts (0.75 mole) ofparaformaldehyde. The desired pro-duct, di-sec.-butyl formaldehydemercaptal, was obtained with 72% yield. The product had an index ofrefraction n of 1.4925.

3,478,107 Patented Nov. 11, 1969 Example 3 The procedure of Example 1was repeated employing 152 parts (2.0 moles) of isopropyl mercaptan and30 parts (1.0 mole) of paraformaldehyde. The desired product,diisopropyl formaldehyde mercaptal, was obtained with 82.5% yield.

The following example illustrates the preparation of a mixture of themercaptals of this invention utilizing a mixed alkyl mercaptan.

Example 4 A mixture of 36 parts (0.4 mole) of tert.butyl mercaptan and36 parts (0.4 mole) of sec-butyl mercaptan is saturated with about0.2-0.4 part of hydrogen chloride. A formalin solution (0.4 mole offormaldehyde) is slowly added over approximately one hour. The reactionis quite exothermic and a temperature of 25-30 C. is maintained bycooling as well as controlling the rate of formalin addition. During theformalin addition, approximately 3-4 parts of HCl gas is added, then thereaction mixture is stirred for 6 hours at 25-30", while HCl gassing iscontinued at the rate of 1.5-2 parts/hour. The total HCl usage isapproximately 13 parts. At the end of the hold period, HCl gassing andstirring is stopped and the lower aqueous layer is: allowed to separate.After drawing off the water layer, the organic layer is washed once with20 parts of water, once with 20 parts of 2.5% lye solution and twicewith 210 parts of water. The crude product is finally stripped at and 30mm. Hg for one hour to provide 73.9 parts of a statistical mixture ofdisec.-butyl formaldehyde mercaptal, di-tert.- butyl formaldehydemercaptal and see-butyl, tert.butyl formaldehyde mercaptal.

The mixed formaldehyde mercaptals of this invention, that is, those inwhich R and R are different alkyl groups, can be prepared in pure form,that is, not in a mixture such as Example 4, by reacting a suitablemercaptan with formaldehyde and HCl to provide a chloromethyl alkylsulfide which in turn is reacted with a sodium mercaptide of a suitablestructure in order to provide the desired compound. A typical procedureof such formaldehyde mercaptals is illustrated by Example 5 below.

Example 5 A mixture of 18 parts (0.2 mole) of tert.-butyl mercaptan, 6parts (0.2 mole) of formaldehyde (as paraformaldehyde) and 30 ml. ofethanol is charged to the flask and cooled to 0 C. Gaseous HCl is passedslowly into the stirred solution maintained at 0", until 7.3 parts (0.2mole) of the acid have been added. The aqueous layer is removed and thetert.-buty1 chloromethyl sulfide recovered by fractionation distillationunder reduced pressure.

To a prepared solution of 4.6 parts (0.2 g. atm s.) of sodium and 40 ml.of ethanol, sec.butyl mercaptan (18 parts, 0.2 mole) and 27.7 parts (0.2mole) of tert.-butyl chloromethyl sulfide are added. Heat is evolvedduring the addition of the chloromethyl sulfide. The resulting mixtureis stirred for an additional 3 hours; after filtration the solvent isstripped under vacuum. The residual product is subjected to vacuumdistillation to provide tert.-butyl, sec.-butyl formaldehyde mercaptal.

Examples of other formaldehyde mercaptals of this invention includeisopropyl-sec.-butyl formaldehyde mercaptal, diisobutyl formaldehydemercaptal, isobutyl, tert.- butyl formaldehyde mercaptal and isobutyl,sec.-butyl formaldehyde mercaptal.

Lubricating oils which can be used as base oils to which theformaldehyde mercaptals of this invention are added include those havinga naphthenic, paraflinic or other hy drocarbon base as well aslubricating oils derived from coal products and also synthetic oils suchas the alkylene polymers, alkenylene oxide polymers, dicarboxylic acidesters, alkylated benzene silicate esters, silicon polymers, polyphenylethers, polyphenyl thioethers and the like. The concentration of themercaptals of this invention in lubricating oils generally used toimprove the antiwear properties of the base oil can range from as low asabout 0.01% to about 10% by weight.

Two tests were utilized to demonstrate the ER or antiwear properties ofthe mercaptals of this invention. These tests were the Four-Ball WearTest and the GMMS (Oldsmobile) Sequence I Test. Utilizing these tests,the following results were noted.

TABLE I Four-ball wear test Mercaptal, Example: Scar diameter, mm.

4 0.40 Base oil 2.13

All tests at 45 kg. loading for 10 minutes at a speed of 1300 r.p.m.Additive concentration was 0.5% by weight.

NOTE-All tests were run at an additive concentration of 0.25% by weight.

Of the formaldehyde mercaptals of this invention, disee-butylformaldehyde mercaptal and see-butyl, tert.- butyl formaldehydemercatpal are outstanding. For example, it has been found that thesec.-butyl, tert.-butyl formaldehyde mercaptal mixture of Example 4shows essentially no increase in average wear in the Sequence I Test toa concentration as low as 0.04% by weight.

From the above, it is clear that the addition to lubricating oils of theformaldehyde mercaptals of this invention brings with it a substantialimprovement in the ER or antiwear qualities of said oils. Nevertheless,the greater proportion of the commercial lubricating oils sold today issubject to a large number of uses and it is, therefore, generallynecessary to employ more than one type of additive in a finishedlubricant formulation. Thus, the mercaptals of this invention can beused in combination with other types of additives such asmetal-containing and/or non-metallic dispersants, corrosion inhibitors,oxide inhibitors, other antiwear agents, viscosity index improvers, pourpoint depressants, anti-foaming agents and the like.

The embodiments of this invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A compound of the structure where R and R are each see-butyl.

2. A compound of the structure RSCH SR where R is sec.-butyl and R istert.-buty1.

References Cited UNITED STATES PATENTS 2,571,114 10/1951 Crouch 260-609OTHER REFERENCES Brown et al.: J. Amer. Chem. Soc. vol. 87 (1965), pp.4559-69.

Levi: Chem. Abstracts, vol. 27, pp. 268-269 (1933).

CHARLES B. PARKER, Primary Examiner D. R. PHILLIPS, Assistant ExaminerUS. Cl. X.R. 25 2--45

